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Re: Using a logical Or in the function definition

  • To: mathgroup at smc.vnet.net
  • Subject: [mg86730] Re: Using a logical Or in the function definition
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Wed, 19 Mar 2008 05:27:53 -0500 (EST)
  • Organization: Uni Leipzig
  • References: <fro39q$i8a$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de

Hi,

ab[r_,s_]/; (IntegerQ[r]|| Head[r]===Rational) && (IntegerQ[s]|| 
Head[s]===Rational):=r/s

??

and all variants of patterns, i.e.,

ab[r_Integer,s_Integer]:=r/s
ab[r_Rational,s_Integer]:=r/s
ab[r_Integer,s_Rational]:=r/s
ab[r_Rational,s_Rational]:=r/s

Regards
   Jens
ahallam at iastate.edu wrote:
> I would like to use Or in the function definition as in
> 
> ab[ Or[r_Integer,r_Rational], Or[s_Integer,s_Rational] ]:=r/s;
> 
> In other words, I want the function to take integers or ratios of
> integers as arguments, but not real numbers which are not rational.
> 
>  But if I give the function integer arguments, it does not evaluate.
> 
> If I try
> 
> ar[ r_Integer , Or[s_Integer , s_Rational]] := r/s;
> 
> and give an integer first argument it works and so on.
> 


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